AIST Researchers Synthesize New n-Type Diamond Semiconductor

Tokyo, Japan -- Dr. Satoshi Yamasaki, a supervising researcher, Dr. Hiromitsu Kato, a researcher, and their colleagues of the Diamond Research Center (DRC), the National Institute of Advanced Industrial Science and Technology (AIST), an independent administrative institution, have succeeded in synthesizing an n-type diamond semiconductor on (001) oriented diamond substrate through the vapor deposition leading the world.

Furthermore, they have successfully realized ultraviolet emission with UV emitting device prepared on the basis of p-n junction using the (001) n-type diamond semiconductor. This is a very significant achievement eliminating the restriction by the substrate orientation, which has been a bottleneck in the development of electron device derived from diamond semiconductor.

- World-first success in synthesizing (001) n-type diamond semiconductor, of great significance for electron device application.
- Ultraviolet emitting diode manufactured on trial basis using p-n junction with (001) n-type diamond semiconductor, successfully emitting UV radiation of 235 nm wavelength.
- A quantum leap toward the practical application of diamond semiconductor, for an electron device.

Diamond is characterized by high thermal conductivity, breakdown voltage and very high mobility for electrons and positive holes, to be promising in the application as electron device based on these merits. Particularly, in the area of power device and short-wavelength light emitting device, the highest performance may be expected among various types of semiconductors, and for this reason, a number of research organizations are racing for the development of diamond semiconductor devices.

For implementing electron device based on diamond semiconductor, it is essential to provide both p-type and n-type semiconductors just like for other kinds of semiconductor. While the p-type diamond semiconductor can be synthesized irrespective of the substrate orientation, that of n-type have been available only for (111) oriented substrate, and never for (001). As the n-type diamond semiconductor on (111) oriented substrate provides a lot of difficulties in the commercialization, it has been urgently requested to synthesize on the (001) oriented substrate.

In the present study, the (001) n-type diamond semiconductor has been synthesized through the microwave plasma chemical vapor deposition process using methane as source gas and doping with phosphorus atoms. The success has been ensured by the difference in phosphorus incorporation in the (001) oriented diamond and from that in the (111), by broadly changing conditions for P-doping and by optimizing the synthetic conditions. Moreover, trial manufacture of UV-emitting device has been achieved by using a good preparation of p-n junction on the (001) oriented substrat, and the emission of UV radiation of 235 nm (1 nm = 10-9 m) wavelength has been confirmed. The UV emission using the (001) n-type diamond semiconductor is also the first success in the world.

SOURCE: AIST